1. A review of the properties of zirconia can be found in E. Ryshkewitch, ?Oxide Ceramics? (Academic Press, New York and London, 1960) p. 350.
2. D. K. Smith and H. W. Newkirk, Acta. Cryst. 18 (1965) 983.
3. P. Duwez, F. H. Brown, and F. Odell, J. Electrochem. Soc. 98 (1951) 360.
4. T. Alper and G. A. Saunders, J. Phys. Chem. Solids 28 (1967) 1637.
5. M. Born and K. Huang, ?Dynamical Theory of Crystal Lattices? (Clarendon Press, Oxford, 1954) p. 141.